FFT of a signal (non constant time)

[mcodesmart]

I took the FFT of a signal that was taken at non constant time period (T), but at a sampling frequency(Fs) of 6.5 hz. Can I take the FFT of a signal with non constant T, and does it mean anything? Please see attachment.

Ps. I used Matlabs, FFT command, which i think uses the Cooley–Tukey FFT algorithm

 

[caffenta]

If the sampling frequency is 6.5Hz, wouldn't that imply a constant time period between samples (153.8msec)? Or what do you mean by T?

 

[mcodesmart]

What I mean is that over all, there are 719 data points taken at a non constant T for a total time period of 111.8 sec. From that, I came up with 6.5, but I see that is misleading.

Here are the timing points..

0.1025, 0.2554, 0.4199, 0.5935, 0.7738, 0.9509 ... 111.80

But signal is clearly periodic so I decided to take the FFT to see the frequencies.. But can I do that..

 

[caffenta]

You could interpolate the data so that it has a constant rate before the FFT with http://www.mathworks.com/help/techdoc/ref/interp1.html".